Serology, idealy Western blott, would be a reasonable test, along with a skin biopsy for PCR . If both of them are negative, borreliosis is a very unlikely diagnosis.
Hello Gulnaz. I have had peronal experience with Western blot kits provided by Biomeca/Virotech and they were of a reasonable quality, with purified and recombinant antigens of Borrelia burgdorferi sensu lato and B. burgdorferi sensu stricto, B. garinii, B. afzelii, B. spielmanii and B. bavariensis. You just need to know, which Borrelia sensu stricto is prevalent in your geografic region. I am afraid, I am not the right person to advise on a PCR test.
As morphea is not recognized as a Lyme disease symptom, you will have to be careful to prove Borrelia burgdorferi s.l. (Bb) to be the etiology. But it is not excluded that you might find a cutaneous infection due to Bb and a morphea. I am not very familiar with clinical aspect of the latter.
If the clinical signs are present for months and serological screening negative for IgG Borreliosis might be reasonably excluded. Negative PCR on a biopsy will add a higher post test exclusion. You might use 2 different PCR choosing different gene as target (flagellin, OspC, 16S rna, etc...)
To prove infection on the other side will need more than a positive serology even if immunoblots of all kinds are confirming your screening, as this diagnostic tool has a very low positive predictive value. Serology utility is often misunderstood and present many pitfalls.
It is then easier to rule out with all negative results, especially when direct diagnostic tools as culture or molecular diagnostic on biopsies are negative. Beware of false positive due to high seroprevalence in a population.
PCR testing is necessary, because there is a significant seroprevalence in elder people. There is a discussion, that morphea is related to borrelia, but it is not generally accepted.